Oct. 13, 1884: Greenwich Resolves Subprime Meridian Crisis

1884: Geographers and astronomers adopt Greenwich as the Prime Meridian, the international standard for zero degrees longitude.

The late 19th century was an era of standardization. With the Second Industrial Revolution stimulating world trade, the Treaty of the Meter established the International System of weights and measures in 1875. With railroads linking together entire continents, nations were replacing hundreds (or even thousands) of diverging local times with a system of hour-wide time zones. (The United States adopted its zones in 1883.)

Amid all this, navigation at sea — and the charting of stars in the heavens — often remained a matter of local, national or even religious preference. Maps might be based on longitude east or west of Jerusalem, Saint Petersburg, Rome, Pisa, Copenhagen (think Tycho Brahe), Oslo, Paris, Greenwich (just east of central London), El Hierro (in the Canary Islands), Philadelphia (former U.S. capital) and Washington, D.C. These divergent reference meridians — representing a mixture of astronomical, theological and maritime power — ranged over 112 degrees of longitude.

Many state boundaries in the U.S. West were determined by the Washington Meridian, which then ran through the Old Naval Observatory in the Foggy Bottom neighborhood. But an 1850 law established its use “for all astronomical purposes, and … the meridian of Greenwich shall be adopted for all nautical purposes.”

In the interests of global amity — and commerce — U.S. President Chester Alan Arthur convened the International Meridian Conference in Washington in 1884. Delegates from 25 countries attended.

The conference set out to select a Prime Meridian for the world. It was really a done deal.

The United States, rising power of the Western Hemisphere, had already adopted the Greenwich Meridian for navigation, and 72 percent of the world’s commerce used nautical charts based on Greenwich.

Britain had first solved the problem of longitude, Britain had the world’s largest navy, and the sun indeed did not set on the far-flung British Empire. Britannia ruled the waves, so there was no need for Britain to waive its rules.

Thus, the conference established that the meridian passing through the Royal Observatory at Greenwich would be the world’s Prime Meridian, and all longitude would be calculated both east and west from it up to 180 degrees. The conference also established Greenwich Mean Time as a standard for astronomy and setting time zones.